The present invention relates to a solid-state imaging device such as a CCD (charge-coupled device) solid-state imaging device or the like and a manufacturing method thereof and a semiconductor device manufacturing method such as a process for forming a metal interconnection, a process for burying a contact-hole or the like.
Generally, in solid-state imaging devices, after electrical components such as charge-transfer regions, channel-stop regions, photo-sensor regions, gate electrodes and so on were formed, a metal film for preventing light from becoming incident on other regions than a photo-sensor region is formed as a light-shielding film.
In conventional solid-state imaging devices, metal thin films such as aluminum, tungsten, tungsten silicide and so on deposited by sputtering have heretofore been used as the light-shielding film. The light-shielding film that was deposited by sputtering is processed by photo-etching to selectively remove the above-mentioned photo-sensor portion only, thereby resulting in pixels of the solid-state imaging device being formed.
However, if the above-mentioned light-shielding film has a poor light-shielding characteristic, i.e. light passes other regions than the photo-sensor region, then light becomes incident on a so-called optical black portion or a phenomenon called a smear in which light is leaked into a charge transfer portion occurs.
If the light-shielding film is thick, then it becomes difficult to process the light-shielding film by microminiaturization or a dark current in the device increases and a point defect increases due to damages caused on the underlayer upon dry etching.
Moreover, if the light-shielding film cannot be reduced in thickness as a size of a pixel is reduced, then a length from an on-chip micro lens to the surface of the photo-sensor increases to lower a lens focusing efficiency of the on-chip micro lens and to thereby lower a photo-sensor sensitivity.
On the other hand, the metal film deposited by sputtering is poor in step coverage and an effective film thickness of a side wall of a step is reduced so that light passes the metal film. Therefore, the film thickness of the metal film cannot be reduced so much. In particular, a leakage of light into the aluminum thin film from a grain boundary is remarkable, and hence the film thickness of the aluminum thin film cannot be decreased up to less than 400 nm.
Since the metal thin film, in particular, the tungsten thin film deposited by a CVD (chemical vapor deposition) which is widely used in the manufacturing process of semiconductors has a considerably satisfactory step coverage in principle, the tungsten film is very effective as the light-shielding film for solid-state imaging devices. However, the tungsten film cannot be directly deposited on a silicon oxide film and is extremely low in adhesion so that an adhesion layer is indispensable for the tungsten film when the tungsten film is deposited on the silicon oxide film. As the adhesion layer, there has hitherto been used a titanium nitride film.
However, since a titanium system material such as a TiN (titanium nitride) film has a function to adsorb hydrogen, the supply of hydrogen from an upper layer to reduce art interface state density of a substrate surface is hindered and the interface state density remains, thereby resulting in a dark current being increased.
Therefore, the titanium material is not suitable as the material of the light-shielding film of the solid-state imaging device.
Since the size of a pixel in a CCD is reduced as a camera is miniaturized recently, there is an increasing demand for a light-shielding film which is strong against the transmission of light and which may be reduced in thickness.